Carbon film

ABSTRACT

Disclosed is a carbon film which has optical characteristics of retaining a high transparency and being high in refractive index and low in double refractivity, is excellent in electric insulating performance, can be applied to various base materials with good adhesiveness, and can be formed at low temperature. Also disclosed is a laminate including a carbon film and a method for producing the laminate.

TECHNICAL FIELD

The invention relates to a carbon film and a laminate having newphysical properties, and an optical device, optical glass, wrist watch,electronic circuit substrate, or grinding tool comprising the same.

BACKGROUND ART

A thin carbonaceous film has various excellent characteristics such ashigh hardness, heat conductivity, electric insulating property,transparency, high refraction index, chemical resistance, low frictionproperty, and low abrasion property. In recent years, coating forimproving the performance of various substrates has been demanded inview of its excellent environmental compatibility and biocompatibility.Particularly, for a diamond-like carbon film or diamond film, as a thincarbonaceous film having excellent physical properties, improvement ofthe coating technique has been expected for enhancing mechanical,optical, and electrical functions of various substrates. However, thediamond-like carbon and diamond involve the following problems due totheir characteristics at present and development of a new carbon filmhas been desired for solving such problems.

In the case of forming a carbon film on a substrate using glass as asubstrate, it has been expected for prevention of injury at the surfacedue to high hardness thereof and application to optical devices havingnew functions due to high refraction index thereof. For example, amethod of forming a microcrystal diamond (hereinafter simply referred toas MCD) film on a glass substrate by a CVD method has already been known(for example, refer to Patent Document 1 and Non-Patent Document 1).

For application as an optical protective film, it has been attempted toutilize the high transmittance of a diamond film. It has been known thatthe transmittance becomes higher as the grain size of the diamondparticles coating the glass surface is smaller and the surface roughnessis smaller. However, according to conventional CVD methods, since theMCD formed has a grain size as large as from 0.3 μm to several μm, theobtained MCD film lacks in the surface planarity and sufficienttransmittance cannot be obtained. For improving the transmittance, it isnecessary to form a planar surface by grinding, and the cost thereforeis one of causes for inhibiting the popularization.

Accordingly, it has been attempted for developing a method of forming aplanar surface without requiring grinding by making the grain size ofthe diamond particles smaller. However, the conventional methods involvea problem that amorphous carbon exhibiting black color intrudessimultaneously with deposition of diamond having small grain size, toresult in a problem of deteriorating the transmittance though thesurface becomes planar.

Further, in the case of utilizing a carbon film coating for a glassprotective film, high adhesion is required. For example, Patent Document1 discloses a method of coating diamond on a glass substrate having agood performance according to a tape test. However, in the applicationuse, for example, in the coating of front glass of an automobile orcoating on a spectacle lens, coating retaining higher adhesion as wellas high transmittance are necessary.

Moreover, for optical application to the lens such as in spectacles,cameras and cinema projectors, it is important that the coating layerhas high refraction index and shows no double refractivity. However, inthe case of utilizing the CVD method as a general coating method, it isextremely difficult to synthesize diamond not showing doublerefractivity in view of thermal strains or residual stresses. Further,the density is often lowered, and the refractive index is usuallylowered considerably. Accordingly, it has been a problem that thediamond coating is not suitable for the optical application.

Additionally, in view of high hardness, and low friction or low abrasioncharacteristic, coating of a thin carbon film to sliding portions ofmechanical parts made of iron or stainless steel as the material hasbeen expected. However, since the coating of the diamond-like carbonfilm or the diamond film to an iron substrate involves a problem that afilm is not deposited due to the intrusion of carbon atoms as theconstituent element of the film into the iron substrate or a problem ofmaking the substrate brittle, practical use thereof is extremelydifficult. On the other hand, an intermediate layer forming method ofcoating the surface of the iron substrate with a thin film of titanium,chromium or a nitride thereof prior to the coating has been developed.However, in view of the problem of requiring a cost for forming theintermediate layer or the problem that the adhesion of the coating isstill low, it has been demanded for the development of a coating insteadof diamond-like carbon or diamond.

In addition, in the case of using copper as a substrate, it is desiredfor coating the diamond-like carbon film or the diamond film to anelectronic circuit substrate having a copper surface in view of the highelectric insulating property thereof. However, deposition of the film tothe surface of copper is extremely difficult. Further, even if it isdeposited, adhesion of the film to the copper surface is low, whichresults in a significant problem that the film tends to be peeled soon.In order to improve this problem, formation of an intermediate layer oftitanium or a nitride thereof has been attempted as in the ironsubstrate described above. However, this also results in a problem forthe occurrence of cost and a problem of low adhesion. Further, in a caseof conducting, particularly, diamond coating by the CVD method which isa usual method, boron in the atmosphere is easily taken into the filmwith no intentional doping, which results in a significant problem thatthe electric insulating property of the diamond coating is lowered.

Further, as a method of coating the carbon film to a plastic substrate,coating of a diamond-like carbon film to a PET bottle has been put topractical use. However, it has been demanded for the coating of plasticswith diamond for the use at a higher temperature and in the opticalutilization. For example, 90% or more of receptacle lenses have beenmade of plastics in recent years. In the case where the diamond coatedplastic spectacle lens can be prepared, it is possible to preventinjuries to the lens or prepare a high functional lens by utilizing thehigh refraction index of diamond. However, synthesis for the diamondfilm requires a high temperature of 600° C. or higher at the lowest and,accordingly, diamond is not suitable at present as a coating materialfor plastics.

-   Patent Document 1: JP-A-10-95694-   Non-Patent Document 1: Diamond and Related Materials vol. 7, pp    1639-1646 (1998)

DISCLOSURE OF THE INVENTION Problem that the Invention is to Solve

The invention has been achieved in view of the foregoing situations inthe current carbon films represented by diamond-like carbon or diamond.That is, an object of the invention is to provide a carbon film and alaminate having optical characteristics of retaining high transparency,having high refraction index and less double refractivity even in a casewhere the particle is smaller, excellent in electric insulatingproperty, capable of being coated at good adhesion irrespective of thekinds of substrates including iron, copper and plastics, and capable ofbeing formed at a low temperature, as well as to provide an opticaldevice, optical glass, wrist watch, electronic substrate, or grindingtool utilizing the same.

Means for Solving the Problem

The present inventors have made earnest studies for the preparation of acarbon film and a laminate having the various characteristics asdescribed above, and as a result, have found that a carbon film and alaminate having excellent performance can be formed by conducting a CVDtreatment under specified conditions and have accomplished the inventionbased on the findings.

Namely, a carbon film of the invention has an approximate spectrum curveobtainable by superimposing, on a peak fitting curve A at a Bragg'sangle (2θ±0.3°) of 43.9°, a peak fitting curve B at 41.7° and a baseline in an X-ray diffraction spectrum by CuKa₁ ray and has a filmthickness of from 2 nm to 100 μm.

The fitting curve A referred to in the present specification is a curveof a Pearson VII function, and the fitting curve B is a curve of anasymmetrical normal distribution function. Further, the base line isrepresented by a primary function.

With regard to the carbon film, the intensity of the fitting curve Brelative to the intensity of the fitting curve A is preferably from 5 to90% in the approximated spectrum described above.

With regard to the carbon film, the Raman shift has a peak at a 1333±10cm⁻¹ and the half-value width of that peak is preferably from 10 to 40cm⁻¹ in the Raman scattering spectrum.

Another carbon film of the invention has an approximate spectrum curveobtainable by superimposing, on a peak fitting curve A at a Bragg'sangle (2θ±0.3°) of 43.9°, a peak fitting curve B at 41.7° and a baseline in an X-ray diffraction spectrum by CuKa₁ ray, wherein the fittingcurve B has an intensity of from 5 to 90% relative to an intensity ofthe fitting curve A, wherein the carbon film has a film thickness offrom 2 nm to 100 μm, and wherein the carbon film has a Raman shifthaving a peak at 1333±10 cm⁻¹, said peak having a half-value width offrom 10 to 40 cm⁻¹ in the Raman scattering spectrum.

The carbon film preferably has a planar surface with the surfaceroughness (Ra) of 20 nm or less.

The carbon film preferably has an electric resistivity of the carbonfilm of 1×10⁷ Ωcm or higher at 100° C. and preferably has an averagetransmittance in a wavelength region of from 400 to 800 nm of 60% ormore.

Further, the carbon film preferably has a refraction index at awavelength of 589 nm of 1.7 or more, and preferably has a doublerefractivity at a wavelength of 589 nm of 1.0 nm or less. Further, thecarbon film preferably has a hardness of 20 GPa or more.

A laminate of the invention comprises a substrate; and a carbonaggregate film having a thickness of 2 nm to 100 μm which is disposed onthe substrate, wherein the carbon aggregate film comprises an aggregateof carbon particles having an approximate spectrum curve obtainable bysuperimposing, on a peak fitting curve A at a Bragg's angle (2θ±0.3°) of43.9°, peak fitting curve B at 41.7° and a base line in an X-raydiffraction spectrum by CuKa₁ ray.

In the present specification, the fitting curve A is a curve of aPearson VII function, the fitting curve B is a curve of an asymmetricnormal distribution curve, and the base line is represented by a primaryfunction.

With regard to the laminate, the carbon particles are preferablyconstituted continuously or discontinuously in the carbon aggregatefilm.

Further, the laminate has a surface density of the carbon particlespreferably within a range of from 1×10¹⁰ cm⁻² to 4×10¹³ cm⁻².

Another laminate of the invention comprises a substrate; and a carbonaggregate film having a thickness of 2 nm to 100 μm which is disposed onthe substrate, wherein the carbon aggregate film comprises an aggregateof carbon particles having an approximate spectrum curve obtainable bysuperimposing, on a peak fitting curve A at a Bragg's angle (2θ±0.3°) of43.9°, a peak fitting curve B at 41.7° and a base line in an X-raydiffraction spectrum by CuKa₁ ray, wherein the fitting curve B has anintensity of from 5 to 90% relative to an intensity of the fitting curveA, wherein the carbon particles have a Raman shift having a peak at1333±10 cm⁻¹, said peak having a half-value width of from 10 to 40 cm⁻¹in the Raman scattering spectrum, and wherein the carbon particles areaggregated on the substrate to give a surface density of from 1×10 cm⁻²to 4×10¹³ cm⁻².

With regard to the laminate, the substrate is, preferably, one memberselected from glass, quartz, silicon, plastic, ceramic, or a group ofmetals such as stainless steel and copper.

With regard to the laminate, the carbon aggregate film preferably has anelectric resistivity of 1×10⁷ Ωcm or higher at 100° C.

With regard to the laminate, the carbon aggregate film preferably has anaverage transmittance of 60% or more to a light having a wavelengthregion of 400 to 800 nm, the carbon aggregate film preferably has arefraction index to a light having a wavelength of 589 nm of 1.7 orhigher, and the carbon aggregate film preferably has a doublerefractivity to a light having a wavelength of 589 nm of 1.0 nm or less.

With regard to the laminate, the carbon aggregate film preferably has ahardness of 20 GPa or more.

Further, with regard to the laminate, adhesion between the glasssubstrate and the carbon aggregate film is preferably 20 GPa or more.

Further, with regard to the laminate, the stainless steel substrate andthe carbon aggregate film preferably have an adhesion strength of 0.3MPa in a flatwise test, and the copper substrate and the copperaggregate film preferably have an adhesion strength of 0.3 MPa or morein a flatwise test.

Further, the invention relates to an optical device, optical glass,wrist watch, electronic circuit substrate, or grinding tool comprisingthe laminate described above.

Effect of the Invention

The carbon film, the carbon particle, and the laminate of the inventionhave optical characteristics of retaining a high transparency, have ahigh refraction index and a small double refractivity even when theparticle is smaller, are excellent in the electric insulating property,can be coated with good adhesion irrespective of the types of thesubstrates including iron, copper, and plastics, and can be formed at alow temperature.

Since the carbon film of the invention has the characteristics describedabove, it can be used in the application such as a protective film forlarge area glass, optical material at high refraction index, highly heatconducting heat sink, electrode material, protection film for machinetool, grinding tool, electron emission material, high frequency device(SAW device), gas barrier coating material, triboelectric material,protective film for cover glass such as in wrist watch and mobiletelephone, biocompatible material, and biosensor.

BEST MODE FOR CARRYING OUT THE INVENTION

The carbon film of the invention, as shown in FIG. 1, has an approximatespectral curve obtainable by superimposing, on a peak fitting curve A ata Bragg's angle (2θ±0.3°) of 43.9°, a peak fitting curve B at 41.7° anda base line in an X-ray diffraction spectrum by CuKa₁ ray, and has afilm thickness of from 2 nm to 100 μm. According to the invention, thefitting curve A is a curve of a Pearson VII function, the fitting curveB is a curve of an asymmetric normal distribution function, and the baseline is represented by a primary function.

It is desirable that the Raman shift has a peak at 1333±10 cm⁻¹, andthat the half-value width of the peak is from 10 to 40 cm⁻¹, accordingto the measurement for the Raman scattering spectral spectrum of thecarbon film. Further, the film has a surface density of the carbonparticles within a range, preferably, of from 1×10¹⁰ cm⁻² to 4×10¹³ cm⁻²and, more preferably, within a range of from 1×10¹¹ cm⁻² to 4×10¹² cm⁻².The surface roughness as Ra is from 2 to 20 nm according to the AFMmeasurement. Further, the film shows a transmittance of 90% or higher inaverage to a visible light (wavelength: 400 to 800 nm) with a filmthickness of 500 nm. Furthermore, the film has an electric resistivityof 1×10⁷ Ωcm or higher at 100° C.

The carbon film of the invention can be obtainable mainly by adoptingspecified production conditions. For preparing the carbon film, it isnecessary for using a surface wave plasma generation apparatus capableof forming a large area film, selecting the concentration, the molarratio of the starting gas, the reaction time, etc. as the operationconditions and conducting operation at a relatively low temperature.

The method of producing the carbon film according to the invention is tobe described for the outline with reference to examples.

For example, fine diamond particles are deposited to a substrate madeof, e.g., glass, silicon, iron, titanium, copper, or plastics by asupersonic treatment, which is applied with a surface wave plasmatreatment by a low-temperature surface wave plasma CVD apparatus using agas containing 98% hydrogen, 1% gaseous carbon dioxide, and 1% methanegas at a pressure of 1×10² Pa.

The treating time is from several hours to several tens hours and thetreating temperature is from 50 to 600° C. By the treatment describedabove, fine carbon particles having a grain size of 2 to 30 nm aredeposited to the surface of the substrate. By making the time longer forthe surface wave plasma treatment, carbon particles are depositedextremely densely with no gaps and a film of 2 μm thickness or more canalso be formed.

Further, fine carbon particles are deposited in a case of the coppersubstrate without deposition of fine diamond particles by a supersonictreatment. Further, when the deposition layer of fine carbon particlesis measured by various film test methods, it has been found that thelayer has outstanding properties such that those having a film thicknessof 500 nm have a transmittance to visible light is 95% or higher,adhesion to the substrate is high, refraction index is high (2.1 orhigher at wavelength of 589 nm), double refractivity is scarcelypresent, surface is planer so as to have a surface roughness (Ra) of 20nm or less in the case of a film of 2 μm thickness, and further, theelectric resistivity at a temperature 100° C. is extremely high so as tobe 10⁷ Ωcm or higher. As described above, the carbon particles and thecarbon film formed by the method have an outstanding performance havinghigh transparency and capability of direct deposition coating also tothe iron or copper substrate.

For producing the carbon film of the invention, it is preferable toprepare the carbon film on the substrate as described above and astypical example of the substrate, glass is used. The glass substrateincludes various kinds of glass conventionally known, such as, soda limeglass or borosilicate glass. The thickness of the glass is notparticularly restricted and it is selected properly in accordance withthe application use of products. It is generally about from 100 to 0.5mm.

According to the invention, at first, nano-crystal diamond particles,cluster diamond particles, or graphite cluster diamond particles aredeposited, or adamantane (C₁₀H₁₆), derivatives thereof, or multimersthereof are deposited to a glass substrate.

Usual nano-crystal diamond particles are diamond prepared by explosionsynthesis, or pulverization of diamond synthesized at high temperatureand high pressure. Cluster diamond particles are aggregates ofnano-crystal diamond particles, and graphite cluster diamond particlesare cluster diamond particles containing a large amount of graphite oramorphous carbon ingredients.

For the nano-crystal diamond, a colloidal solution formed by dispersingnano-crystal diamond obtainable by explosion synthesis in a solvent hasbeen marketed from the NanoCarbon Research Institute Ltd. ornano-crystal diamond powder prepared by pulverization, or dispersionthereof in a solvent has been already marketed, for example, from TomeiDiamond Co. Ltd. The nano-crystal diamond particles used in theinvention have an average grain size of 4 to 100 nm, preferably, from 4to 10 nm. The nano-crystal diamond is described specifically, forexample, in the literature “Hiroshi Makita, New Diamond vol. 12, No. 3,pp 8-13 (1999)”.

For depositing the nano-crystal diamond particles on the glasssubstrate, the particles are dispersed in water or ethanol. In thiscase, for improving the dispersibility, a surfactant (for example,sodium salt of lauryl sulfate ester, sodium oleate, etc.) is added, asubstrate is dipped in the liquid dispersion and put to a supersoniccleaning apparatus and then the substrate is dipped in ethanol toconduct supersonic cleaning and then the substrate is taken out anddried.

As described above, a glass substrate with deposition of nano-crystaldiamond particles on the surface can be obtained. Deposition of thenano-crystal diamond particles to the glass substrate is attained byburying of a portion of the particles to the surface of the substratedue to physical force in the supersonic cleaning treatment.

The deposition ratio of the nano-crystal diamond particles to thesubstrate surface is, preferably, from 10⁹ to 10¹², more preferably,from 10¹⁰ to 10¹¹ per 1 cm². The diamond particles deposited to theglass substrate act as seed crystals for the growth of the carbon filmin the surface wave plasma treatment.

In this case, the deposition ratio of the nano-crystal diamond particlesdeposited on the substrate surface can be decreased by decreasing theconcentration of the nano-crystal diamond particles to be dispersed in adispersion medium (water, ethanol, etc.). This can lower the density forthe occurrence of nuclei of the carbon particles in the surface waveplasma treatment to obtain not a continuous film but a discontinuousfilm comprising an accumulation body of carbon particles. The surfacedensity of the carbon particles in the accumulation body can becontrolled by the concentration of the nano-crystal diamond particles inthe liquid dispersion. Further, the grain size of the carbon particlescan be controlled by the time of conducting the surface wave plasmatreatment. An accumulation body comprising carbon particles isolated onthe substrate can be prepared by decreasing the concentration extremely.Further, by treating the accumulation body with hydrofluoric acid or thelike to remove the substrate from the accumulation body, only the carbonparticles can also be obtained.

Furthermore, an identical deposition effect with that by the supersoniccleaning method can be obtained by spin coating the liquid dispersion ofthe nano-crystal diamond on the substrate and then drying the same,which is another method of depositing the nano-crystal diamond particlesin the substrate.

The cluster diamond particles are aggregates of the nano-crystal diamondprepared by the explosion synthesis method, which are excellent in thetransparency and already sold, for example, from Tokyo Diamond ToolsMfg. Co., Ltd., etc. According to the cluster diamond particles used inthe invention, the grain size distribution is, preferably, from 4 to 100nm and, more preferably, from 4 to 10 nm. The cluster diamond particlesare described in details in the document “Hiroshi Makita, New Diamond,vol. 12, No. 3, p 8 to 13 (1996)”.

For depositing the cluster diamond particles on the glass substrate, theparticles are dispersed in water or ethanol. In this case, for improvingthe dispersibility, a surfactant (for example, sodium salt of laurylsulfate ester, sodium oleate, etc.) is added, a substrate is dipped inthe liquid dispersion and put to a supersonic cleaning apparatus, thenthe substrate is dipped in ethanol to conduct supersonic cleaning, andthen the substrate is taken out and dried.

As described above, a glass substrate with deposition of cluster diamondparticles on the surface can be obtained. Deposition of the clusterdiamond particles to the glass substrate is attained by the burying of aportion of the particles in the surface of the substrate due to thephysical force in the supersonic cleaning treatment. The depositionratio of the cluster diamond particles to the substrate surface is,preferably, from 10⁹ to 10¹², more preferably, from 10¹⁰ to 10¹¹ per 1cm². The diamond particles deposited to the glass substrate act as seedcrystals for the growth of the carbon film in the surface wave plasmatreatment.

In this case, deposition ratio of the cluster diamond particlesdeposited to the substrate surface can be decreased by decreasing theconcentration of the cluster diamond particles to be dispersed in adispersion medium (water, ethanol, etc.). This can lower the density forthe generation of nuclei of the carbon particles in the surface waveplasma treatment to obtain not a continuous film but a discontinuousfilm comprising an accumulation body of carbon particles. The surfacedensity of the carbon particles in the accumulation body can becontrolled by the concentration of the cluster diamond particles in theliquid dispersion. Further, the grain size of the carbon particles canbe controlled by the time for conducting the surface wave plasmatreatment. Further, an accumulation body comprising isolated carbonparticles can be prepared on the substrate by decreasing theconcentration extremely. Further, by treating the accumulation body withhydrofluoric acid or the like to remove the substrate from theaccumulation body, only the carbon particles can also be obtained.

Further, an identical deposition effect with that by the supersoniccleaning method can be obtained by spin coating the liquid dispersion ofthe cluster diamond on the substrate and then drying the same, which isanother method of depositing the cluster diamond particles on thesubstrate.

For depositing the graphite cluster diamond particles on the glasssubstrate, the particles are dispersed in water or ethanol. In thiscase, for improving the dispersibility, a surfactant (for example,sodium salt of lauryl sulfate ester, sodium oleate, etc.) is added, asubstrate is dipped in the liquid dispersion and put to a supersoniccleaning apparatus, then the substrate is dipped in ethanol to conductsupersonic cleaning, and then the substrate is taken out and dried.

As described above, a glass substrate with deposition of graphitecluster diamond particles on the surface can be obtained. Deposition ofthe graphite cluster diamond particles to the glass substrate isattained by the burying of a portion of the particles in the surface ofthe substrate due to the physical force in the supersonic cleaningtreatment.

The deposition ratio of the graphite cluster diamond particles to thesubstrate surface is, preferably, from 10⁹ to 10¹² and, more preferably,from 10¹⁰ to 10¹¹ per 1 cm². The diamond particles deposited to theglass substrate act as seed crystals for the growth of the carbon filmin the surface wave plasma treatment.

In this case, the deposition ratio of the graphite cluster diamondparticles deposited to the substrate surface can be decreased bydecreasing the concentration of the graphite cluster diamond particlesto be dispersed in a dispersion medium (water, ethanol, etc.). This canlower the density for the occurrence of nuclei of the carbon particlesin the surface wave plasma treatment to obtain not a continuous film buta discontinuous film comprising an accumulation body of carbonparticles. The surface density of the carbon particles in theaccumulation body can be controlled by the concentration of the graphitecluster diamond particles in the liquid dispersion. Further, the grainsize of the carbon particles can be controlled by the time forconducting the surface wave plasma treatment. Further, an accumulationbody comprising isolated carbon particles can be prepared on thesubstrate by decreasing the concentration extremely. Further, bytreating the accumulation body with hydrofluoric acid or the like toremove the substrate from the accumulation body, only the carbonparticles can also be obtained. Further, in a case of preparing acontinuous film on the substrate, a self-sustaining film can be preparedby the removal of the substrate.

Furthermore, an identical deposition effect with that by the supersoniccleaning method can be obtained by spin coating the liquid dispersion ofthe graphite cluster diamond on the substrate and then drying the same,which is another method of depositing the graphite cluster diamondparticles on the substrate.

Adamantane is a molecule represented by the molecular formula: C₁₀H₁₆,which is a sublimating molecular crystal having the same stericstructure as the basic skeleton of diamond (at normal temperature,normal pressure), and is produced by the purification process ofpetroleum. Powders thereof, derivatives thereof, and multimers thereofhave already been sold by Idemitsu Kosan Co., LTD.

In order to deposit adamantane, derivatives thereof, or multimersthereof on a glass substrate, the substance is dissolved in a solvent(for example, ethanol, hexane, acetone nitrile, etc.), then thesubstrate is dipped in the solution and subjected to supersonic cleaningand, subsequently, the substrate is taken out and dried. As describedabove, a glass substrate deposited at the surface thereof withadamantane, derivatives thereof, or multimers thereof can be obtained.

In this case, the deposition ratio of adamantane, derivatives thereof,or multimers thereof deposited on the substrate surface can be decreasedby decreasing the concentration of adamantane, derivatives thereof, ormultimers thereof to be dispersed in a solvent. This can lower thedensity for the occurrence of nuclei of the carbon particles in thesurface wave plasma treatment to obtain not a continuous film but adiscontinuous film comprising an accumulation body of carbon particles.The surface density of the carbon particles in the accumulation body canbe controlled by the concentration of adamantane, derivatives thereof,or multimers thereof in the liquid dispersion. Further, the grain sizeof the carbon particles can be controlled by the time for conducting thesurface wave plasma treatment. Further, an accumulation body comprisingisolated carbon particles can be prepared on the substrate by decreasingthe concentration extremely. Further, only the carbon particles can alsobe obtained by treating the accumulation body with hydrofluoric acid orthe like to remove the substrate from the accumulation body.

Furthermore, an identical deposition effect with that by the supersoniccleaning method can be obtained by spin coating the solution of thesubstance on the substrate and then drying the same, which is anothermethod of depositing adamantane, derivatives thereof, or multimersthereof on the substrate.

Then, according to the invention, a treatment is applied to a glasssubstrate deposited at the surface thereof with diamond particles, oradamantane, multimers thereof, or derivatives thereof obtained asdescribed above (hereinafter simply referred to also as a glasssubstrate), by using a microwave plasma CVD apparatus.

The microwave plasma CVD apparatus (hereinafter also referred to simplyas CVD apparatus) has already been known and is available, for example,from Applied Films Corporation. FIG. 3 shows the outline of the CVDapparatus. FIG. 4 shows the constitution of a reaction vessel thereof.

For applying the CVD treatment to the glass substrate, it is necessaryto conduct the treatment at a temperature lower than the distortionpoint of the glass substrate. Since the pressure is from 2×10³ to 1×10⁴Pa in the usual CVD treatment for diamond, the substrate temperatureexceeds 800° C. and the treatment cannot be applied to the glasssubstrate. In order to lower the temperature, plasma treatment at a lowpressure is necessary. For this purpose, in the invention, a surfacewave plasma is generated under a pressure of about 1×10² Pa, which wasutilized for the CVD treatment. The surface wave plasma is describedspecifically, for example, in the literature “Hideo Sugai, PlasmaElectronics, Ohmusha Ltd., 2000, p. 124 to 125”. This can lower the CVDtreatment temperature for the glass substrate to a temperature lowerthan the distortion point and plasmas can be generated uniformly over alarge area of 380 mm×340 mm or more. As a result of diagnosing theplasmas by a Langmure probe method (single probe method), it isconfirmed that the plasma density is 8×10¹¹/cm³ and this exceeds acritical plasma density of 7.4×10¹⁰/cm³ as the condition for the surfacewave plasma with a microwave at a frequency of 2.45 GHz. The Langmureprobe method is described specifically, for example, in the literature“Hideo Sugai, Plasma Electronics, Ohmusha Ltd., 2000, p. 58”.

As the conditions for the CVD treatment used in the invention, atemperature, preferably, from 50 to 600° C., more preferably, from 300to 450° C. and a pressure, preferably, from 5×10¹ to 5×10² Pa and, morepreferably, from 1.0×10² to 1.2×10² Pa are used. The treating time is0.5 to 20 hours and, usually, about 1 to 8 hours. By the treatment time,a film thickness of about 100 nm to 2 μm is obtained.

The starting gas (reaction gas) used for the CVD treatment is a gasmixture comprising a carbon-containing gas and hydrogen. Thecarbon-containing gas includes, for example, methane, ethanol, acetone,and methanol.

The concentration of the carbon-containing gas in the carbon-containinggas/hydrogen gas mixture is from 0.5 to 10 mol %, and preferably, from 1to 4 mol %. In the case where the amount of the carbon-containing gas ismore than the range described above, it is not preferred since thiscauses a problem such as lowering of transmittance.

Further, CO₂ or CO is preferably added to the gas mixture as an additivegas. The gas acts as an oxygen source and shows an effect of removingimpurities in the CVD treatment.

The addition amount of CO₂ and/or CO is preferably from 0.5 to 10 mol %,and more preferably, from 1 to 4 mol % in the entire gas mixture.

In the case of applying the CVD treatment to the glass substrateaccording to the invention, in view of the adhesion between the glasssubstrate and the synthesized carbon film, the CVD treatment temperature(substrate temperature) is controlled desirably to a temperature lowerthan the distortion point of glass, preferably, to a low temperature ofabout 300 to 450° C. For example, in the case of a soda lime glasssubstrate, since the distortion point thereof is about at 470° C., theCVD treatment temperature therefore is a temperature lower than that,preferably, at 300 to 450° C. For a borosilicate glass such as Pyrex(registered trademark), the CVD treatment temperature is preferably from400 to 550° C., and more preferably, from 450 to 500° C.

According to the invention, carbon particles or a carbon film can beformed on the glass substrate. The carbon particles and the carbon filmhave a remarkable feature different from other carbon particles andcarbon films of diamond, etc., in that they have an approximate spectrumcurve obtainable by superimposing, on a peak fitting curve A at a Braggangle (2θ±0.3°) of 43.9°, a peak fitting curve B at 41.7±0.30 and a baseline in an X-ray diffraction spectrum by CuKa₁ ray, as shown in FIG. 1.

Further, in the Raman scattering spectral spectrum, (excitation lightwavelength: 244 nm) a distinct peak is observed near the Raman system1333 cm⁻¹ and the full width half-value maximum (FWHM) is from 10 to 40cm⁻¹. Further, in the case of the film, it is excellent in the planarityand the adhesion, and the surface roughness Ra is 20 nm or less and itis planar as reaching 3 nm or less depending on the case. Further, ithas optically excellent properties being excellent in the transparency,having a refraction index as high as 2.1 or more and scarcely showingdouble refractivity, and also has excellent electric properties such asshowing a high electric insulating property with the resistivity beingas high as 10⁷ Ωcm or higher at a temperature of 100° C.

Further, from the observation for the film cross section by a highresolution power transmission type electronic microscopy, it is found tobe characteristic that crystalline carbon particles with the grain sizeof 1 nm to several tens nm are formed with being packed without gaps andthe grain size distribution does not change at the interface between thefilm and the substrate, in the film, and near the uppermost surface ofthe film (average grain size is substantially equal). The thickness ofthe carbon film thus obtainable is preferably from 2 nm to 100 μm, andmore preferably, from 50 to 500 nm, and the grain size of the particleis preferably from 1 to 100 nm, and more preferably, from 2 to 20 nm.

Example

The present invention is to be described more specifically. However, theinvention is no way restricted by such examples.

As a substrate, glass (borosilicate glass and soda lime glass) cut outto 300 mm×300 mm was used. Further, for manufacturing a specimen forevaluation, a wafer-like glass substrate of 4 inch diameter was alsoused. For increasing the density of nuclear formation of the carbonparticles and forming a uniform film, a pre-treatment (depositiontreatment of nano-crystal diamond particles) was conducted to thesubstrate before film formation.

A colloidal solution in which nano-crystal diamond particles of anaverage grain size of 5 nm were dispersed in pure water (manufactured bylimited company, Nanocarbon Research Institute Ltd., products name:Nanoamand), a solution in which nano-crystal diamond particles of anaverage grain size of 30 nm or 40 nm were dispersed in pure water(manufactured by Tomei Diamond Co. Ltd., products name, MD30 and MD40respectively), ethanol in which cluster diamond particles or graphitecluster diamond particles (manufactured by Tokyo Diamond Tools Mfg. Co.,products name, CD, GCD respectively) dispersed in ethanol, or a solutionof adamantane, derivatives thereof, or derivatives thereof (eachmanufactured by Idemitsu Kosan Co., Ltd.) was used, to which a substratewas dipped and put to a supersonic cleaning apparatus.

Then, the substrate was dipped in ethanol and applied with supersoniccleaning and dried, or the solution is coated uniformly on a substrateby spin coating and dried. The uniformness by the pre-treatment gives aneffect on the uniformness of the carbon film after film formation. Inthis case, the number of diamond particles deposited on the substratewas from 10¹⁰ to 10¹¹ per 1 cm².

As the starting gas, CH₄, CO₂, and H₂ were used and the concentration ofCH₄ and CO₂ were defined each as 1 mol %. The gas pressure in thereactor was controlled to 1.0 to 1.2×10² Pa (1.0 to 1.2 mbar) lower thana pressure used for the usual CVD synthesis of diamond (10³ to 10⁴ Pa),and microwave of 20 to 24 kW in total was charged to generate plasmasfor a large area and uniformly over a region larger than the substratearea (300×300 mm²). In this case, an Mo specimen table and a coolingstage were in close contact with each other and the distance between thesubstrate and the antenna was adjusted making it possible to keep thesubstrate temperature to 450° C. or lower during film formation which isthe softening point of soda lime glass.

Film formation was conducted for 6 to 20 hours under the film formingconditions described above. A uniform and transparent carbon film wasformed on the glass substrate after film formation. The thickness of thefilm was from 300 nm to 2 μm.

FIG. 5 shows a schematic photograph for a carbon film formed on a glasssubstrate of 300 mm×300 mm according to the invention. In FIG. 5, thesubstrate appears as if it were distorted because of the function of acamera but the substrate is not actually distorted. The film has athickness of about 400 nm and is extremely transparent but presence ofthe film can be confirmed by interference color.

The carbon film was observed by X-ray diffraction. Details for themeasurement are to be described. The X-ray diffraction apparatus used isan X-ray diffraction measuring apparatus RINT2100 XRD-DSCII manufacturedby Rigaku Corporation and a goniometer is ultima III horizontalgoniometer manufactured by Rigaku Corporation. A multi-purpose specimentable for thin film standard was attached to the goniometer. Themeasured specimen is a carbon film of 500 nm thickness prepared on aborosilicate glass substrate of 1 mm thickness by the method asdescribed above. Those cut out to 30 mm square together with the glasssubstrate were measured. As X-rays, copper (Cu) Ka₁ rays were used. Thevoltage and current applied to the X-ray tube were 40 kV and 40 mA. Ascintillation counter was used for an X-ray detector. At first, thescattering angle (2θ angle) was calibrated by using a silicon standardspecimen. Deviation of 2θ angle was +0.02° or less. Then, the measuringspecimen was set to the specimen table and the 2θ angle was adjusted to0°, i.e., the X-ray incident direction and the specimen surface were inparallel and one-half of the incident X-rays is shielded by thespecimen. The goniometer was rotated from the state and X-rays wereirradiated at an angle of 0.5° relative to the specimen surface. The 2θangle was rotated at 0.02° step from 10° to 90° while fixing theincident angle, and the intensity of X-rays scattering from the specimenat 2θ angle for each of them was measured. A computer program used forthe measurement is RINT2000/PC software Windows (registered trademark)version.

FIG. 1 shows a measured spectrum of X-ray diffraction. Blanc circles inthe graph are measuring point. It can be seen that a distinct peak ispresent at 2θ of 43.9°. It is interesting, as can be seen from FIG. 1,that the peak at 43.9° has a shoulder at 2θ of 41 to 42° on the lowerangle side thereof (for “shoulder” of the spectrum, refer to “KagakuDaijiten (Chemical Encyclopedia)” (Tokyo Kagaku Dojin). Accordingly, thepeak comprises a two-component peak having a peak (first peak) about at43.9° as a center and another peak (second peak) distributed about at 41to 42°. In X-ray diffraction by CuKa₁ rays, diamond has been known as acarbonaceous substance having a peak at 2θ of 43.9°. FIG. 2 is aspectrum measured for diamond by X-ray diffraction and the peak isattributable to (111) reflection of diamond. Difference of theX-diffraction spectrum between the carbon film of the invention anddiamond is clear, and the second peak distributed about at 41 to 42°appearing in the spectrum of the carbon film of the invention cannot beseen in diamond. As described above, (111) reflection of diamondconsists of the first component (only the first peak) at 43.9° as thecenter in which shoulder on the lower angle side as in the carbon filmof the invention is not observed. Accordingly, the second peakdistributed about at 41 to 42° observed in the spectrum of the carbonfilm of the invention is a peak inherent to the carbon film of theinvention.

Further, it can be seen that the peak for the X-ray diffraction spectrumof the carbon film of the invention in FIG. 1 is much broaden whencompared with the peak of diamond in FIG. 2. Generally, as the size ofparticles constituting the film decreases, the width of the X-raydiffraction peak is widened more and the size of the particlesconstituting the carbon film of the invention can be said to beextremely small. When the size of the carbon particle constituting thecarbon film of the invention (average diameter) is estimated based onthe width of the peak according to the Sherrer's formula usually used inthe X-ray diffraction, it was about 15 nm. For the Sherrer's formula,refer, for example, to “Hakumaku (Thin Film) Handbook, edited by JapanSociety for the Promotion of Science, Thin Film, 131st Committee, fromOhmusha Ltd., in 1983, p. 375”.

Then, details for the constitution of the peak (positions and strengthfor respective peak ingredients) are to be considered.

For determining the detailed constitution of the peak at 2θ of 43.9° inthe X-ray diffraction measurement for the carbon film of the invention,analysis was conducted for 2θ angle from 39° and 48° by using peakfitting. For the fitting of the first peak, a function called as aPearson VII function was used. The function is used most generally asrepresenting the profile of peak in the diffraction method such as X-raydiffraction or neutron diffraction. The Pearson VII function can bereferred to “Introduction Practice of Powder X-ray Analysis—Introductionto Rietveld Method” (edited by X-ray Analysis Study Conference of JapanSociety for Analytical Chemistry, Asakura Shoten). Further, as a resultof study for various functions, it has been found that an asymmetricfunction is preferably used for the fitting of the second peak. In thisexample, an asymmetric normal distribution function (Gaussiandistribution function) was used. The function is a normal distributionfunction having separate dispersion (standard deviation) values on theright and the left of the peak position, which is one of most simplestfunctions as a function used for the fitting of an asymmetric peak, andcould fit to peak extremely favorably. Further, a linear function(primary function) was used as a base line (background) function.

While various computer programs can be utilized for actual fittingoperation, ORIGIN version 6, peak fitting module Japanese edition(hereinafter as ORIGIN-PFM) was used. In ORIGIN-PFM, the Pearson VIIfunction is represented as “Pearson 7”, the asymmetric normaldistribution function is represented as “BiGauss”, and the linearfunction is represented as “line”. The completion condition for fittingis defined such that the correlation coefficient representing thereliability of the fitting (“COR”, or “Corr Coef” in ORIGIN-PFM) was0.99 or more.

According to the analysis using the peak fitting, as shown in FIG. 1, itcan be seen that the measured spectrum can be approximated well as thesum for the first peak according to the Pearson VII function (fittingcurve A in the graph), a second peak according to the asymmetric normaldistribution function (fitting curve B in the graph) and the base lineaccording to the primary function (background) (total fitting curve inthe graph). In the measurement, the center for the fitting curve A is at2θ of 43.9°, while the fitting curve B has a maximum at 41.7°. Areassurrounded by respective fitting curves and the base line are respectivepeak intensities. Thus, the intensity of the second peak to theintensity of the first peak was analyzed. In the case of this specimen,the intensity of the second peak (fitting curve B) was 45.8% for theintensity of the first peak (fitting curve A).

When X-ray diffraction measurement was conducted for many specimens ofthe carbon film of the invention, a broad peak as shown in FIG. 1 wasobserved around 2θ of 43.9° as the center for all of the specimens. Inaddition, they were in a shape having a shoulder on the lower angle sideas shown in FIG. 1, and comprised of the first peak and the second peak.When analysis was conducted by the same peak fitting for the X-raydiffraction spectrum measured for many specimens, it was found thatfitting could be conducted well by using the functions described above.The center for the first peak was at 2θ of 43.9±0.3°. Further, it wasfound that the second peak had a maximum at 2θ of 41.7±0.3°. Theintensity ratio to the first peak was 5% at the minimum and 90% at themaximum. The intensity ratio had large dependence on the synthesistemperature and it tended to increase as the temperature was lower. Onthe other hand, the peak position was substantially constantirrespective of the synthesis temperature.

What is to be noted for the analysis method of the X-ray diffractionmeasurement is that measured data scatter greatly as the intensity ofthe X-ray is smaller and no reliable fitting is possible. Accordingly,it is necessary to conduct the analysis by the fitting for those havingthe maximum intensity of the peak of 5000 counts or more.

As described above, it was found that the carbon film of the inventionhas a broad peak around 2θ of 43.9° as the center in the measurement ofX-ray diffraction by CuKa₁ rays, and that the peak had a structure witha shoulder on the lower angle side. It was found by the analysis usingthe peak fitting that the peak could be approximated well bysuperimposing the first peak using the Pearson VII function having acenter at 2θ of 43.9°, the second peak using the asymmetric normaldistribution function being maximum at 41.7°, and the base line with theprimary function (background).

Analysis by fitting was conducted in the same manner for the spectrum ofdiamond shown in FIG. 2. It was found that the peak could beapproximated well only with the Pearson VII function having a center at2θ of 43.9° in a case of diamond, quite different from the carbon filmof the invention described above. Accordingly, it was found that thecarbon film of the invention was a substance having a structuredifferent from that of diamond.

The carbon film of the invention has a feature in that the second peakdescribed above is observed and this is a carbon film having a structuredifferent from that of diamond. The production step of the carbon filmof the invention and the result of other measurements were studied andthe structure was investigated. The synthesis method of the carbon filmused in the invention has the following remarkable feature when comparedwith the CVD synthesis method for diamond. At first, while usualsynthesis for the diamond has been conducted at a temperature of atleast 700° C. or higher, the carbon film of the invention is synthesizedat an extremely low temperature. Further, in a case of decreasing thegrain size of the diamond film, a method of rapidly growing at a highconcentration of about 10% for the concentration of the carbon source(molar ratio of methane gas) contained in the starting gas has beenemployed so far, the concentration of the carbon source is rather low asabout 1%. That is, in this method, carbon particles are deposited at alow temperature extremely slowly for a long time to form a film.Accordingly, the carbon particles are deposited at a breaking situationwhere they are transformed to diamond or not. Accordingly, a force ofpromoting deposition of hexagonal system diamond which is carboncrystals more stable than the usual cubic system diamond or depositionof further stable graphite, and this is extremely instable as the stateof crystal deposition. Further, once deposited graphite and amorphouscarbonaceous substance are also removed by etching by a great amount ofhydrogen plasmas contained in the starting gas. By means of such adeposition mechanism, they form a structure in which cubic systemdiamond and hexagonal system diamond are mixed, and portions removed byetching remain as defects at an extremely high concentration. Suchdefects are point defects as atomic vacancy, linear defects asrelocation, or defects on the basis of the surface unit such aslamination defects are also contained in a great amount. Accordingly, itforms a structure in which X-ray diffraction peak at 43.9° has ashoulder on the lower angle side.

However, the feature of the X-ray diffraction peak described above is inassociation with high function of the carbon film of the invention. Thatis, while a structure containing defects at high concentration is formedsince etching for graphite or graphite like substance is promoted due tothe low speed synthesis at a low concentration of the carbon source, thetransparency of the carbon film is kept high. Further, while the cubicsystem diamond and the hexagonal system diamond are mixed and defects ata high concentration are contained due to synthesis at high temperature,carbon is deposited with no penetration also to the iron substrate andcan also be coated directly on copper. Further, the size of fineparticles is aligned due to synthesis at low temperature and thermalstrain is extremely small. That is, the structure in which the cubicsystem diamond and the hexagonal system diamond are mixed and defects atan extremely high concentration are contained results in a feature thatthe thermal strain is moderated and the optical double refractivity issmall. Further, an extremely high electric insulating property isdeveloped by virtue of the structure in the same manner.

Measurement of Raman scattering spectral spectrum was conducted for thecarbon film. An ultraviolet excitation spectrometer, NRS-1000Vmanufactured by Jasco International Co., Ltd. was used for themeasurement and a UV-laser at a wavelength of 244 nm was used for theexcitation light (Ar ion laser 90C FreD manufactured by Coherent Inc.)was used. The power of the laser source was 100 mW and a beam attenuatorwas not used. An aperture was set to 200 μm. Measurement for twice withexposure time of 30 sec and 60 sec was accumulated to obtain a spectrum.The apparatus was calibrated with single crystal diamond synthesized athigh temperature and high pressure as a standard specimen for Ramanscattering spectroscopy (DIAMOND WINDOW Type: DW006 for Raman, Material:SUMICRYSTAL, manufactured by Sumitomo Electric Industries Ltd). The peakposition of the Raman spectrum in the standard specimen was adjusted toRaman shift of 1333 cm⁻¹. A computer software, Spectra Manager forWindows (registered trademark) 95/98 ver. 1.00 manufactured by JascoInternational Co., Ltd. for the standard of this apparatus was used forthe measurement and the analysis.

FIG. 6 shows a typical measured Raman scattering spectral spectrum. Themeasured specimen is a carbon film of about 1 μm thickness prepared on aborosilicate glass wafer of 10 cm diameter and 1 mm thickness by themethod described above. As seen in FIG. 6, a peak situated near theRaman shift of 1333 cm⁻¹ was distinctly observed in the Raman scatteringspectrum of the carbon film. As a result of conducting measurement inthe same manner also for many other specimens, it was found that thepeak was within a range from 1320 to 1340 cm⁻¹ and always in a range of1333±10 cm⁻¹. Further, a broad peak appearing near the Raman shift of1580 cm⁻¹ showed the presence of the sp² bond component of carbon. Asthe ratio of the component increases, the film becomes not transparentblack. In the case of FIG. 6, the height of peak was as low as about 1/7compared with the height of peak at 1333 cm⁻¹ and as shown below, it wasfound that the film was a transparent film. The Full Width atHalf-Maximum (FWHM) in this case was about 22 cm⁻¹. As a result of thesame measurement also for many other specimens, it was found that FWHMwas within a range from 10 to 40 cm⁻¹.

The cross section of the carbon film was observed by a high resolutiontransmission type electron microscope (HRTEM). The HRTEM apparatus usedwas H-9000 transmission electron microscope manufactured by Hitachi Ltd.and observation was conducted at an acceleration voltage of 300 kV.Further, a standard fitted specimen holder of the HR-TEM apparatus wasused for the specimen holder. The specimen for observation wasmanufactured by any one of methods (1) slicing by an Ar ion millingtreatment, (2) slicing by converging ion beam (FIB) fabrication, or (3)peeling the film surface with a diamond pen and collecting the obtainedslice to a microgrid.

FIG. 7 shows an example of the result of observation. FIG. 7 is anexample of observation for the film cross section on a glass substrate.In this case, the specimen was manufactured by the ion millingtreatment. FIG. (a) is an interface between the film and the substrate,FIG. (b) is the outermost surface of the film, FIG. (c) is electrondiffraction images of the film, and FIG. (d) shows the result ofmeasurement for electron energy loss spectral (EELS) spectrum at theabsorption edge of carbon K shell of carbon particles constituting thefilm. It can be seen from FIGS. (a) and (b) that lattice images areobserved substantially over the entire surface of the film and the filmis thoroughly buried with crystalline particles with no gaps. Further,electron beam diffraction images in the FIG. (c) are close to a ringpattern of polycrystal diamond at random alignment. However, diffractionspots not riding on one ring are contained in a great amount in a ringparticularly corresponding to the diamond (111) face and they correspondto diffraction by a plane larger by 2 to 6% than the diamond (111) facein view of inter-planar spacing. The diamond film is remarkablydifferent from usual diamond in this regard. Further, crystal grainswith the grain size from 1 nm to several tens nm are packed without gapsand the grain size distribution does not change for the interfacebetween the film and the substrate, in the film, and in the vicinity forthe uppermost surface of the film. Further, it was observed that oneparticle comprises one or more crystallites. Further, it can be seenfrom EELS spectrum in FIG. d, that there are scarce peaks correspondingto σ-σ* transition showing the presence of C-C sp² bond but a peakcorresponding to s-s* showing the presence of the sp³ bond component ispredominant. That is, it can be seen that the film comprises crystallinecarbon particles comprising sp³ bonded carbon atoms.

The crystallite is a microcrystal that can be regarded as a singlecrystal and generally one grain comprises one or plurality ofcrystallites. From the result of HRTEM observation, the size (averagegrain size) of the carbon particles (crystallites) in the film is notdifferent for the interface with the substrate, in the film, and at theuppermost surface, which was within a range from 2 to 40 nm.

In a case where it could be regarded that the film was constituted withparticles packed with no gaps, the average grain size was determined inaccordance with the following procedures.

That is, the average grain size was decided in a transmission typeelectron microscopic photograph for the cross section of a carbon filmby taking the average of the grain size for different particles(crystallites) by the number of at least 100 or more. In FIG. 7( a), aportion surrounded with a white closed curve is one particles and thearea surrounded with the closed curve is determined and, assuming thevalue as S, the grain size D was decided as:D=2√ S/πin which π represents the circle ratio.

Further, the surface density d_(s) of the particle is determined basedon the average grain size of the particles according to:d _(s)=unit area/(π×(average grain size/2)²)

When the surface density of the carbon film of the invention isdetermined as described above, it has been found that this is notdifferent for the interface, in the film, and at the uppermost surfaceand, it is within a range from 8×10¹⁰ cm⁻² to 4×10¹² cm⁻².

The carbon film was observed under a scanning type electron microscope(SEM). After forming a carbon film of about 500 nm thickness on aborosilicate glass substrate of 10 cm diameter and 1 mm thickness as aspecimen, the substrate was cracked and the substrate was inclined andthe cross section thereof was observed. For preventing charge-up causedby the glass substrate and the diamond film each being a dielectricmaterial, a relatively low acceleration voltage of 1 kV was used and itwas observed at a relatively low magnification factor of about 7000×.FIG. 8 shows the result of observation. As seen in FIG. 8, the film wasextremely planar and no distinct unevenness was observed at all at themagnification factor.

The surface of the carbon film was observed by an atomic forcemicroscope (AFM) to evaluate the surface roughness. In this case, forsuppressing the effect of the surface roughness of the substrate on thesurface roughness of the film as less as possible, the film was formedon a mirror-polished quartz disk (10 mm diameter×3 mm thickness) withless surface roughness (arithmetic average height Ra=0.9 to 1.2 nm) andused as a specimen for measurement. The AFM apparatus used was a nanoscope scanning type probe microscope manufactured by Digital InstrumentsCorporation and a canti-lever Nanoprobe Type NP-1 for use in scanningtype probe microscope manufactured by Digital Instruments Corporation,was used as the canti-lever. A tapping mode was used for measurement andobservation was conducted at a scanning size of 1 μm and at a scanningrate of 1.0 Hz.

FIG. 9 shows the result of observation for the film surface by an atomicforce microscope (AFM). For the image processing for the result ofobservation and the evaluation for the surface roughness, themeasurement and analysis computer software, Nanoscope III ver. 4.43r8 asthe standard for AFM apparatus was used. By the analysis for the resultof the observation, the surface roughness Ra of the film was 3.1 nm.Evaluation was also conducted for many other specimens and it wasconfirmed that the surface roughness was within a range of 2.6 to 15 nmas Ra while different depending on the deposition condition of the film.Also for the evaluation of the surface roughness of the quartz disksubstrate before deposition of the film, measurement was conducted inthe same manner and it was found that it was within a range from 0.9 to1.2 nm as Ra.

The arithmetic average height Ra is described specifically, for example,in “JIS B 0601-2001” or “ISO 4287-1997”.

Transmittance of the carbon film to a visible light was measured. As aspecimen, a carbon film according to the invention formed on aborosilicate glass wafer substrate of 10 cm diameter and 1 mm thicknesswas used. As a transmittance measuring apparatus, UV/Vis/NIRSpectrometer Lambda 900 manufactured by Perkin Elmer Inc. was used andtransmittance was measured in a wavelength region of from 300 nm to 800nm. In the measurement, a light from a light source was divided into twooptical channels, and one was applied to the specimen formed with thefilm and the other was applied to a glass substrate not formed with thecarbon film. Thus, the transmittance spectrum of the specimen and thatof the glass substrate were measured simultaneously, and thetransmittance spectrum of the carbon fiber per se was determined bysubtracting the spectrum of the glass substrate from the spectrum of thespecimen. For measurement and analysis, UV-Winlab ver. X1.7Amanufactured by Perkin Elmer Inc. as a computer software for measurementand analysis for the apparatus was used.

FIG. 10 shows an example of the measured transmission spectrum of thefilm. The thickness of the film was about 500 nm. When the averagetransmittance at a wavelength of from 400 nm to 800 nm in a visiblelight region was determined from the spectrum, the transmittance wasabout 90% and it was found that the transparency was extremely high as anot polished carbon film. Particularly, it has been found that the filmhad an outstandingly high transmittance even compared with a general notpolished thin diamond film.

The refractive index of the carbon film was measured by phase differencemeasurement. A specimen prepared by forming the carbon film according tothe invention on a borosilicate glass wafer substrate of 10 cm diameterand 1 mm thickness and cutting out the substrate into 20 mm square wasused. A phase difference measuring apparatus NPDM-1000 manufactured byNicon Corporation was used as a measuring apparatus and M-70 was used asa spectralizer. A xenon lamp was used as a light source, and Si—Ge wasused as a detector. Further, Gramthomson was used as a polarizer and ananalyzer, with the number of rotation of the polarizer being set to 1.Measurement was conducted at an incident angle of 65° and 60°, at ameasuring wavelength of 350 to 750 nm and, at a 5 nm pitch. The measuredphase difference D and the spectrum of the amplitude reflectance y werecompared with calculation models to fit such that they approached themeasured values (D, y), and the refraction index, the extinctioncoefficient, and the film thickness were decided based on the result ofthe best fitting between the measured values and the theoretical values.Calculation was conducted assuming that each layer of the specimen wasan isotropic medium.

FIG. 11 shows the wavelength dependence of the refraction index and theextinction coefficient in the measurement for the phase difference. Theresult of evaluation for the film thickness was about 440 nm. It wasfound from FIG. 11 that the film had a high refraction index of 2.1 ormore in the entire wavelength region of measurement. Further, therefraction index at the wavelength of 589 nm [Sodium D ray] was about2.105.

The double refractivity of the carbon film was measured. A specimenprepared by forming the carbon film according to the invention on aborosilicate glass wafer substrate of 10 cm diameter and 1 mm thicknessand cutting out the substrate into 20 mm square was used. Measurementwas conducted by a phase difference measuring method, and a phasedifference measuring apparatus NPDM-1000 manufactured by NiconCorporation was used as a measuring apparatus, M-70 was used as thespectralizer and a halogen lamp was used as a light source. Further,Si—Ge was used as the detector, and Gramthomson was used as a polarizerand an analyzer. Measurement was conducted at a number of rotation of 1for the polarizer at an incident angle each of 0°, for wavelength regionof 400 to 800 nm at a 5 nm pitch. Further, the dependence on the angleof rotation was measured at a wavelength of 590 nm.

Measurement was conducted in an arrangement shown in FIG. 12. In FIG.12, a specimen was rotated, a phase difference D=DS−DP (difference for Spolarized light and p polarized light) was monitored at the angle ofrotation, and wavelength dispersion measurement was entered with anangle showing the maximum phase difference as the direction of themaximum phase difference. The measuring light was incident on the sideof a diamond film. Further, the measuring wavelength for the dependenceof angle of rotation was 590 nm. Measurement was conducted in the samemanner also for the borosilicate glass used for the substrate, which wascompared with the glass substrate formed with the carbon film, by whichdouble refractivity of the carbon film was evaluated.

FIG. 13 shows typical examples of the result of the measurement. In thiscase, the thickness of the carbon film was about 200 nm. At first as aresult of measuring the dependence of the phase difference on the angleof rotation, it showed substantially identical dependence with that ofborosilicate glass used for the substrate. The maximum phase differencedirection was determined based on the measurement, and the specimen wasrotated in this direction to measure the phase difference and thewavelength dispersion at Dnd. FIG. 13 shows the result of measurement.FIG. (a) shows the wavelength dispersion of the phase difference andFIG. (b) shows a calculation value for Dnd (nm)=wavelength (nm)×phasedifference/360. Both FIGS. (a) and (b) show a difference spectrumobtained by subtracting the measured value or the calculated value onlyof the glass substrate. From the graphs, it can be seen that the phasedifference and Dnd are substantially 0 and that the film scarcely showsthe double refractivity.

A test for the close adhesion of the carbon film to the glass substratewas conducted. A specimen prepared by forming carbon film of a filmthickness of about 280 nm, 600 nm and 2.2 μm respectively on aborosilicate glass wafer substrate of 10 cm diameter and 1 mm thicknessand cutting out respective substrates each into about 20 mm square wasused.

A flatwise test was conducted for the three specimens to evaluate theadhesion strength. A universal material tester Model 5565 manufacturedby Instron Corporation was used for a measuring apparatus and a crosshead moving amount method was used for a measuring method. A jig wasbonded by an adhesive to each of the diamond film and the glasssubstrate of the specimens, an adhesion strength test (flatwise test)was conducted by a cross head moving amount method at a measuringtemperature equal to room temperature (23° C.) to obtain aload-displacement diagram. A load upon initial fracture was read basedon the obtained graph, and the adhesion strength was evaluated based onthe value obtained by dividing the same with an adhesion area. The testwas conducted at a speed of 0.5 mm/min. Further, data processing system“Merlin” manufactured by Instron Corporation was used for the dataprocessing.

As the result of measurement, since peeling did not occur at theinterface between glass and carbon film and peeling occurred at theinterface between the adhesive and the jig in any of the specimens, theadhesion strength between glass and film could not be evaluated.However, it was found that the adhesion strength was at least 0.30 MPaor more.

Then, adhesion of the film to the glass substrate was evaluated by ascratch method using a Nano Indenter scratch option. In the adhesionevaluation by the scratch method, the surface of the specimen wasscratched while applying a load on a diamond indenter (in other words,the specimen was scratched while indenting the diamond indenter therein)and it was evaluated by a vertical load when the film was peeled(critical peeling load).

As a measuring apparatus, Nano Indenter XP manufactured by MTS SYSTEMSCORPORATION was used, and Test Works 4 manufactured by MTS SYSTEMSCORPORATION was used as a computer software for measurement and analysisfor the standard of the apparatus. XP (diamond Cube corner type) wasused for the indenter (Tip). Measurement was conducted at a maximumindentation load of 20 to 250 mN, at a profile load of 20 μN, with ascratch distance of 500 μm, for the number of measuring points of 10,with an inter-measuring point distance of 50 μm, and at a measuringcircumstance temperature of 23° C. (room temperature).

The maximum indentation load was determined by conducting an indentationtest before the scratch test, and estimating a load to reach thesubstrate based on a load-displacement (indentation depth) curve.

The profile load is a load applied to an indenter upon scanning thespecimen surface with a minute load (profile step) before the scratchtest in order to detect the state of the specimen surface.

A specimen for measurement prepared by forming the diamond filmaccording to the invention on a borosilicate glass wafer substrate of 10cm diameter and 1 mm thickness, and cutting out the substrate into about10 mm square was used. The specimen was set to a specimen table by usinga crystal bond (hot melting adhesive) to conduct measurement.

The scratch test is conducted by the following three steps.

First step: Surface profiling with a minute load

The surface state is detected by the step.

Second step: Profile just before profile→scratch→profile just after

Scratch test is conducted while actually applying a load by the step.

Third step: Surface re-profile

The surface property for scratch flaws can be recognized by the step.

The steps are conducted on every measuring points, and the adhesionstrength is evaluated as scratch hardness on every measuring points.

FIG. 14 shows an example of the result of the scratch test at a certain1 measuring point for a carbon film of 600 nm thickness. In FIG. 14, theabscissa represents the scratch resistance and the ordinate representsthe indentation depth. The maximum indentation load in this case was 20mN. The graph shows three steps in the measurement. In the figure, theindentation depth increases abruptly between the scratch distance of 500nm and the final point, and this is a typical example of the peelingphenomenon. The scratch hardness H of the specimen is determined basedon the peeling starting point as described below.H=P/Ain which P is a vertical load at the peeling position and A is an areaof contact at the peeling start point. A is estimated as:A=2.5981×ht²/3 (ht: indentation depth at the peeling start point).

As described above, the scratch test was conducted on 10 measuringpoints of each specimen, an average was taken for meaningful measuringresults, which was determined as a scratch hardness of the specimen. Ina case of the specimen shown in FIG. 14, it was found that the scratchhardness reached 110 GPa and the adhesion was extremely high. Further,the standard deviation of the scratch hardness was about 6.2 withextremely less variation depending on the measuring points.

Further, for other specimens (film thickness about 280 nm) the carbonfilm did not peel even when the indenter reached the substrate, whichshowed such an intense adhesion as cannot be evaluated by the evaluationmethod.

For recognizing the electric characteristic of the carbon film accordingto the invention, electric resistance measurement and hole resistancemeasurement were conducted. Details for the measurements are to bedescribed below. An electric resistance measuring apparatus and a holeeffect measuring apparatus used were Resi Test Model 8310S equipmentmanufactured by Toyo Corporation. Further, a specimen holder used wasmodel VHT manufactured by Toyo Corporation. The measured specimen was acarbon film of 500 nm thickness prepared on a Pyrex (registeredtrademark) glass substrate of 1 mm thickness by the method describedabove. Those cut out together with the glass substrate each into 4 mmsquare were measured. Ti was deposited to a circular shape of 0.3 mmdiameter by vacuum vapor deposition to four corners of the specimen asan electrode. Further, Pt was vapor deposited to 50 nm and Au was vapordeposited to 100 nm thereon to prevent oxidation of the Ti electrode.The electrode was heat treated in an argon atmosphere at 400° C.intended for stabilization. This was attached to a specimen table madeof high resistance alumina, and wiring was conducted by supersonicbonding of a gold wire having a φ of 250 μm to the electrode.

Measurement for the electric resistance was conducted in an atmosphereof helium at 1 mbar. Measurement was conducted each at 25° C. step froma room temperature up to 400° C.

FIG. 15 shows the temperature dependence of the electric resistivity ofthe specimen. At 100° C. or lower it had extremely high resistance,exceeding 1×10⁹ Ωcm as the upper limit of the possible measuring rangeof the measuring equipment and no accurate measurement was possible. Byextrapolation of measuring data at 100° C. or higher, it is consideredthat the electric resistivity at the room temperature is 1×10¹⁰ Ωcm orhigher. Further, also at 400° C., it showed a resistance value as highas 1×10³ Ωcm or higher.

While it was tried to determine the electroconductivity type by the holeeffect measurement, it could not be judged whether it was p-type orn-type due to the high resistance.

The electrical properties as described above show that the carbon filmof the invention functions as an extremely excellent electric insulatingfilm.

A carbon film was tried to be formed on a glass substrate at a substratetemperature of 100° C. or lower according to the invention. A surfacewave plasma CVD treatment was conducted at a substrate temperature ofabout 95° C. for 7 hours. A borosilicate glass wafer of 10 cm diameterand 1 mm thickness was used for the substrate. A transparent film wasformed on the substrate after the CVD treatment. The film was measuredfor the Raman scattering spectrum by the method described above. Theresult is shown in FIG. 16. From the graph, a peak showing diamond atRaman shift 1333 cm⁻¹ was distinctly observed and a full width at ahalf-maximum was about 25 cm⁻¹. Thus, it was found that a carbon filmcould be formed on the glass substrate by the method according to theinvention even at a processing temperature of 100° C. or lower.

Carbon films were formed on glass substrates other than borosilicateglass and, further, on substrates other than glass such as of metals andplastics. Specifically, the following substrates were used.

Glass

Soda lime glass: 150×150×t5 mm and 300×300×t3 mm

Quartz: φ10×t2 mm and 50×26×t0.1 mm

Metal

Copper: 20×20×t3 mm, 150 mm×150 mm×t2 mm and 300×300×t3 mm

Iron: 20×20×t3 mm and 150 mm×150 mm×t2 mm

Stainless steel (SUS 430): 20×20×t2 mm and 150 mm×150 mm×t2 mm

Titanium: φ10×t2 mm

Molybdenum: φ30×t5 mm

Aluminum: 20×20×t2 mm and 150 mm×150 mm×t2 mm

Super hard alloy: φ30×t5 mm

Plastic

Polyether sulfon (PES): 20×20×t1 mm

Others

Silicon (single crystal (001) face): φ100×t5 mm

After the surface wave plasma CVD treatment, a diamond film was formedon each of the substrates. FIG. 17 shows Raman scattering spectra of thefilms formed on the substrates. The Raman scattering spectralmeasurement was conducted by the method described above. For each of thespectra, a peak was observed near the Raman shift at 1333 cm⁻¹.

For the diamond films on the copper substrate and the stainless steelsubstrate, the adhesion strength was evaluated by a scratch test.Measurement was identical with the evaluation for the scratch hardnessby the scratch method using the Nano Indenter scratch option describedabove. The specimen used for the evaluation was a copper substrate of20×20×t3 mm and a stainless steel (SUS 430) substrate of 20×20×t2 mmeach formed with the diamond film, and the thickness of the diamond filmwas about 600 nm in each of them. The maximum indentation load in thiscase was 1 mN for the film on the copper substrate and 10 mN for thefilm on the stainless steel substrate. Other measuring conditions werequite identical with those for the method described above.

As a result of conducting the scratch test, the film did not causepeeling even when the indenter was indented by 1 μm which was largerthan the film thickness and the evaluation for the adhesion strength wasdifficult. However, since it did not cause peeling even at theindentation depth larger than the film thickness, it can be consideredthat the adhesion is extremely excellent.

The hardness in the carbon film of the invention was measured by using anano indenter. As a measuring apparatus, Nano Indenter XP manufacturedby MTS SYSTEMS CORPORATION was used and measuring and analyzing computersoftware, Test Work 4 ver. 4.06A manufactured by MTS SYSTEMSCORPORATION. for the standard of the apparatus was used for themeasurement and analysis. XP was used for the indenter (Tip).

A specimen for measurement prepared by forming the carbon film accordingto the invention on a single crystal (001) wafer substrate of 10 cmdiameter and 1 mm thickness and cutting out the substrate to 10 mmsquare was used. In this case, the thickness of the carbon film wasabout 2.5 μm. The specimen was fixed to a specimen table by using acrystal bond (hot melting adhesive) to conduct measurement.

FIG. 18 shows the result of measurement for the hardness of the carbonfilm. The maximum indentation depth was 300 nm. Further, measurement wasconducted at a room temperature (23° C.). As can be seem from the graph,it was found that the hardness of the carbon film reached as high as 100GPa and it had a hardness substantially equal with that of usualdiamond.

According to the method of the invention, a discontinuous carbon filmcomprising aggregates of carbon particles according to the invention wasformed on the substrate. Upon depositing nano diamond particles, clusterdiamond particles, graphite cluster diamond particles, adamantane,derivative thereof, or multimers thereof on the substrate beforeconducting the surface wave plasma CVD treatment according to the methodof the invention, the deposition density of them to the substrate can bedecreased by extremely lowering the concentration of them to adispersion medium or a solvent for dispersing or dissolving them. Thiscan lower the surface density for the generation of nuclei of diamondupon CVD treatment and can form not a continuous film but adiscontinuous film on the substrate. In this case, the grain size of thecarbon particles constituting the discontinuous film can be controlleddepending on the time for the surface wave plasma CVD treatment (thesize is smaller as the time is shorter and the size is larger as thetime is longer).

FIG. 19 shows an optical microscopic photograph for the discontinuouscarbon film thus formed in this way on the borosilicate glass substrate.An optical microscope, LEITZDMR manufactured by Leica Co. was used forobservation. For taking the photograph, digital camera DFC 280manufactured by Leica Co. as the standard of the microscope and 1M50ver. 4.0 Release 117 as the photographing and analyzing compute softwarewere used. Further, in this case, a borosilicate glass wafer substrateof 10 cm diameter and 1 mm thickness was dipped in a liquid dispersionin which graphite cluster diamond particles were dispersed extremelythinly in ethanol (concentration: about 0.01 wt %) before the filmdeposition treatment, and pre-treatment was conducted by supersonictreatment. Subsequently, a surface plasma CVD treatment was conductedfor about 7 hours. The average grain size of the diamond particles shownin FIG. 19 was about 3 μm. In this case it is considered that a singleparticle is an aggregate of carbon particles (crystallites) by thenumber of 200 in average. The surface density of particles in this casewas about 5×10⁶ cm⁻², which was considered to be substantially equalwith the deposition density of the graphite cluster diamond particlesdeposited to the substrate by the pre-treatment.

The discontinuous film comprising the carbon particle aggregates shownin FIG. 19 contains a number of isolated carbon particles on the glasssubstrate and carbon particle powder can be obtained in a case of thediscontinuous carbon particle powder by removing the substrate byhydrofluoric acid treatment or the like.

As shown in FIG. 20, the carbon film of the invention was laminated on aquartz glass plate and the operation thereof as a grinding tool wasconfirmed. The tested quartz glass had 30 mm φ and 1 mm thickness and acarbon film of the invention was deposited to a thickness of 500 nm onthe surface to form a laminate. The surface of the quartz glass waspolished before deposition of the carbon film and it was confirmed bythe observation under an atomic force microscope (AFM) that it had aplanarity of about 1 mm as surface roughness Ra. A titanium plate wasrubbed frictionally for 100 cycles reciprocally to the laminate and thechange of Ra before and after thereof was measured by AFM. While Ra ofthe titanium plate before rubbing was 100 nm, Ra after rubbing was 20 nmto confirm the improvement of the planarity. It was confirmed that thelaminate using the carbon film of the invention functions as a grindingtool.

The carbon film of the invention was laminated on glass and the opticalconfinement effect was demonstrated. The carbon film of the inventionwas deposited to a thickness of 200 nm on the surface of usual slideglass (25 mm×75 mm, about 1 mm thickness) to form a laminate. FIG. 21shows a structure of an optical device. When a light was entered from amercury lamp at an angle of about 45° from one end to the surface of thecarbon film of the laminate, light was emitted from the other end apartby 40 mm. Thus, it could be confirmed that the light from the mercurylamp incident from one end of the carbon film repeats total reflectionat the boundary surface between the carbon film and the slide glass andat the boundary surface between the carbon film and air, and ispropagated while being confined as far as the other end. As describedabove, it was found that the carbon film of the invention can beutilized as an optical device such as an optical waveguide channel byutilizing the high refraction index.

The carbon film of the invention was coated on glass to demonstrate theflaw preventive effect. The carbon film of the invention was coated to300 nm thickness on the surface of borosilicate glass of 10 cm diameterand 1 mm thickness. Then, it was rubbed by #1000 sand paper for 100cycles reciprocally. The result is shown in FIG. 22( a). Further, FIG.22( b) is a photograph showing the result of conducting an identicaltest for borosilicate glass not coated with the carbon film of theinvention. As shown, glass coated with the carbon film of the inventionwas scarcely injured. On the other hand, glass not coated with thecarbon film of the invention was injured. As described above was foundthat the carbon film of the invention shows high flaw preventive effectfor optical glass. Accordingly, coating of the carbon film of theinvention enables application use, for example, to optical glass,lenses, and spectacles with improved flaw-preventive effect.

A carbon film of the invention was deposited to 300 mm thickness onquartz glass and a wrist watch having the same for wind proofness wasformed as shown in FIG. 23, to demonstrate the function as flawprevention for a wind proof body. The surface of the wind proof memberwas rubbed with #1000 sand paper for 100 cycles reciprocally, it was notinjured at all. As described above, it was confirmed that a wrist watchhaving a laminate of the carbon film and the quartz glass of theinvention as a wind proof has a characteristic that the wind proofsurface is less injured.

A carbon film of the invention of 500 nm thickness was deposited on athin aluminum plate of 0.3 mm thickness to form a laminate and, further,an electronic circuit pattern was formed with copper on the carbon filmto prepare an electronic circuit substrate. FIG. 24 is a schematic viewfor the electronic circuit substrate. It was confirmed that the electricinsulating property of copper and aluminum putting the carbon filmtherebetween was extremely excellent. The substrate may not only bealuminum but other materials. It has been confirmed that the laminateusing the carbon film of the invention functions as an electroniccircuit substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an X-ray diffraction spectrum of a carbon film as anexample of the invention by CuKa₁ X rays, and the result of peakfitting. In the drawing, blank circles show measured values.

FIG. 2 shows a typical X-ray diffraction spectrum of diamond by CuKa₁X-rays ((111) reflection peak), and a result of peak fitting. In thedrawing blank circles show measured values.

FIG. 3 is an appearance of a microwave plasma CVD apparatus for largearea deposition used in the invention.

FIG. 4 shows the constitution of a reaction vessel of a microwave plasmaCVD apparatus of a microwave plasma CVD apparatus for large areadeposition used in the invention.

FIG. 5 is a photograph of a carbon film formed on a glass substrate (300mm×300 mm) according to the invention.

FIG. 6 is a Raman scattering spectral spectrum chart of a carbon film asan example of the invention.

FIG. 7 is a photograph of a high resolution transmission type electronmicroscope (HRTEM) for the cross section of a carbon film on a glasssubstrate according to the invention. FIG. (a) shows a boundary surfacebetween a glass substrate and a carbon film, FIG. (b) shows theoutermost surface of the carbon film, FIG. (c) shows electron beamrefraction images of the carbon film and FIG. (d) is an electron energyloss spectral (EELS) spectrum view (C-K shell absorption edge).

FIG. 8 is a scanning type electron microscopic photograph for the crosssection of a carbon film as an example formed on a glass substrateaccording to the invention.

FIG. 9 is an atomic force microscope (AFM) photograph for the surface ofa carbon film (1.6 μm thickness) formed on a quartz substrate (Ra=0.87nm) according to the invention.

FIG. 10 is a wavelength dispersion graph of a transmittance in a visiblelight region of a carbon film (about 500 nm thickness) of an exampleformed on a glass substrate according to the invention.

FIG. 11 is a wavelength dispersion graph of a refraction index and anextinction coefficient of a carbon film of an example formed on a glasssubstrate according to the invention.

FIG. 12 is a schematic view showing a double refraction measuring methodfor a carbon film of an example formed on a glass substrate according tothe invention.

FIG. 13 is a wavelength dispersion graph of phase difference and of acarbon film (about 200 nm thickness) of an example formed on a glasssubstrate according to the invention. In the data in the graph, measuredvalues only for the glass substrate are subtracted from measured valuesfor the glass substrate formed with the carbon film.

FIG. 14 shows an example of the result of measurement at a certainmeasuring point in a scratch test of a carbon film (about 600 nmthickness) as an example formed on a glass substrate in the invention.The abscissa represents the scratch distance and the ordinate representsthe indentation depth in the graph.

FIG. 15 is a graph showing the dependence of the electric resistivity onthe temperature of one example of the carbon film (about 500 nmthickness) formed on the glass substrate according to the invention.

FIG. 16 is a Raman scattering spectrum chart of one example of a carbonfilm formed on a glass substrate at a low substrate temperature of 100°C. or lower (about 95° C.) according to the invention).

FIG. 17 shows Raman scattering spectral charts of one examples of acarbon film formed on various kinds of substrates according to theinvention. Substrate are (a) Si, (b) quartz glass, (c) Ti, (d) WC, (e)Cu, (f) Fe, (g) soda lime glass, (h) stainless steel (SUS 430), and (i)Al, respectively.

FIG. 18 is a graph showing the result of measurement for hardness by aNano Indenter of one example of a carbon film formed on a siliconsubstrate according to the invention.

FIG. 19 is an optical microscopic photograph of one example ofdiscontinuous carbon film particles formed on a glass substrateaccording to the invention.

FIG. 20 shows a polishing tool including a carbon film of the inventionand quartz glass.

FIG. 21 shows an optical device including a carbon film of the inventionand glass.

FIG. 22 is a photograph showing the glass protective film effect of thecarbon film of the invention. FIG. (a) shows borosilicate glass coatedwith a carbon film of the invention and FIG. (b) shows borosilicateglass without coating. Both FIGS. (a) and (b) show photographs for thetrace after rubbing with sand paper (#1000) for 100 cycles reciprocally.

FIG. 23 shows a wrist watch having a laminate including a carbon film ofthe invention and quartz glass as a wind shield.

FIG. 24 is a schematic view of an electronic circuit substrate obtainedby forming an electronic pattern with copper on a laminate including analuminum plate and a carbon film according to the invention.

1. A carbon film, which has an approximate spectrum curve obtainable bysuperimposing, on a peak fitting curve A at a Bragg's angle (2θ±0.3°) of43.9°, a peak fitting curve B at 41.7° and a base line in an X-raydiffraction spectrum by CuKa₁ ray, said fitting curve B having anintensity of from 5 to 90% relative to an intensity of the fitting curveA, said carbon film having a film thickness of from 2 nm to 100 μm, saidcarbon film having a Raman shift having a peak at 1333 cm⁻¹±10 cm⁻¹,said peak having a half-value width of from 10 to 40 cm⁻¹ in the Ramanscattering spectrum, wherein the fitting curve A is a curve of a PearsonVII function, the fitting curve B is a curve of an asymmetric normaldistribution function, and the base line is represented by a primaryfunction, wherein said carbon film comprises a structure in which acubic diamond and a hexagonal diamond are mixed and a defect remains ata high concentration in a portion removed by etching, and a peak isobserved at 2θ of 43.9°±0.3° in the X-ray diffraction spectrum in thecubic diamond and a peak is observed at 2θ of 41.7°±0.3° in the X-raydiffraction spectrum in the defect, wherein the crystal defect compriseshexagonal diamond and a point defect including atomic vacancy, a lineardefect including relocation or a defect on the basis of a surface unitincluding a lamination defect, and wherein the defect is formed in aportion formed by removing a graphite or amorphous carbonaceoussubstance deposited in the course of the film formation by etching. 2.The carbon film according to claim 1, which has a Raman shift having apeak at around 1580 cm⁻¹ in the Raman scattering spectrum based on sp²bond component of carbon derived from a component including a graphiteor amorphous carbonaceous substance.
 3. The carbon file according toclaim 1 wherein a surface density of the carbon is 8×10¹⁰ cm⁻² to 4×10¹²cm⁻².
 4. A laminate comprising: a substrate; and a carbon aggregate filmhaving a thickness of 2 nm to 100 μm which is disposed on the substrate,said carbon aggregate film comprising an aggregate of carbon particleshaving an approximate spectrum curve obtainable by superimposing, on apeak fitting curve A at a Bragg's angle (2θ±0.3°) of 43.9°, a peakfitting curve B at 41.7° and a base line in an X-ray diffractionspectrum by CuKa₁ ray, said fitting curve B having an intensity of from5 to 90% relative to an intensity of the fitting curve A, said carbonparticles having a Raman shift having a peak at 1333±10 cm⁻¹, said peakhaving a half-value width of from 10 to 40 cm⁻¹ in the Raman scatteringspectrum, said carbon particles being aggregated on the substrate togive a surface density of from 1×10¹⁰ cm⁻² to 4×10¹³ cm⁻², wherein thefitting curve A is a curve of a Pearson VII function, the fitting curveB is a curve of an asymmetric normal distribution curve, and the baseline is represented by a primary function, wherein said carbon filmcomprises a structure in which a cubic diamond and a hexagonal diamondare mixed and a defect remains at a high concentration in a portionremoved by etching, and a peak is observed at 2θ of 43.9°±0.3° in theX-ray diffraction spectrum in the cubic diamond and a peak is observedat 2θ of 41.7°±0.3° in the X-ray diffraction spectrum in the defect,wherein the crystal defect comprises hexagonal diamond and a pointdefect including atomic vacancy, a linear defect including relocation ora defect on the basis of a surface unit including a lamination defect,and wherein the defect is formed in a portion formed by removing agraphite or amorphous carbonaceous substance deposited in the course ofthe film formation by etching.
 5. The laminate according to claim 4,wherein the substrate is a member selected from the group consisting ofglass, quartz, silicon, plastic, ceramic, a metal and a metal alloy. 6.The laminate according to claim 5, wherein the substrate is glass, andwhich has an adhesion between the glass substrate and the carbonaggregate film of 20 GPa or more.
 7. The laminate according to claim 5,wherein the substrate is stainless steel, and wherein the stainlesssteel substrate and the carbon aggregate film have an adhesion strengthof 0.3 MPa in a flatwise test.
 8. The laminate according to claim 5,wherein the substrate is copper, and wherein the copper substrate andthe carbon aggregate film have an adhesion strength of 0.3 MPa in aflatwise test.
 9. The laminate according to claim 4 wherein a surfacedensity of the carbon is 8×10¹⁰ cm⁻² to 4×10¹² cm⁻².